The power saving mode of a station associated with an access point in a wireless local area network (WLAN) operating under IEEE 802.11 standards may be coordinated through the use of the traffic indication map (TIM) information element (IE) contained in the periodic beacons transmitted by the access point. Data transmitted by the access point may be characterized based upon whether the traffic is directed to a single station or to a group of stations. For example, unicast traffic includes packets addressed to a single station within the WLAN, while group traffic includes multicast data that is addressed to a plurality of stations, broadcast data that is addressed to all stations or both multicast data and broadcast data.
Each beacon transmitted by the access point includes TIM information regarding unicast traffic, allowing a station to determine whether to poll the access point to initiate transfer of data that has been buffered. Delivery of group traffic, on the other hand, is not initiated by the stations. Rather, a subset of the beacons, known as delivery TIM (DTIM) beacons, are transmitted at a periodicity advertised by the access point and may be used to indicate that group traffic has been buffered at the access point and will be transmitted following the DTIM beacon. Accordingly, a station typically will be configured to awaken in order to receive the DTIM beacon and may remain awake to receive the data when the DTIM beacon indicates there is buffered group traffic.
However, situations may exist wherein a station may want to receive only one type of group traffic, either multicast data or broadcast data, but not both. A DTIM beacon conforming to 802.11 standards does not distinguish between types of group traffic. Thus, the station may need to stay awake to receive the group traffic since it may be unable to determine from the DTIM beacon whether the data buffered corresponds to multicast or broadcast data, even though the traffic may be of a type that is not currently of interest. Consequently, the power consumed by the station during reception of the group traffic may represent an unnecessary expenditure. A station may have a limited power supply, as exemplified by battery-powered mobile stations such as smartphones, making it desirable to avoid power consumption that does not contribute to the overall performance of the station.
Accordingly, there is a need for systems and methods for coordinating delivery of multicast and broadcast data in a manner that conserves power. Further, there is a need for distinguishing between multicast and broadcast traffic to allow a station to avoid receiving an unwanted type of group traffic. This disclosure satisfies these and other needs.